Alternator loading engine

Thread Starter

Denny B

Joined Aug 30, 2022
11
Hi, I'm new here. I searched the Internet looking for a solution to my problem and stumbled upon this Forum. Maybe you guys and help me.

I am building a small yard buggy which originally was a golf cart. It had no engine when I got it. I have installed a one cylinder, 6.5 horsepower engine in it. The buggy runs fine for what I intend to use it for.

Now, here's my problem. I have installed headlights on the buggy plus an electric starter for the engine. The battery is a 12v motorcycle battery. I purchased a "mini", 35-amp alternator to run the lights and charge the battery. The alternator creates a heavy load on the engine. It cranks slow when starting (because of heavy drag/load) and the engine idles very rough. When I disconnect the alternator wire from the battery the engine smooths right out and runs just fine.

I have realized the alternator is creating a heavy load on the small 6.5 hp engine so I started looking for a smaller alternator and thanks to Google I came across permanent magnet alternators which then led me to this Site and this thread. :)

Is a PMA the answer to my problem? Will it create little or no drag on the engine?

Thank you.
 

LowQCab

Joined Nov 6, 2012
4,290
No .......
A permanent Magnet Alternator is used because it's cheap to manufacture, and that's the only reason.

An Automotive-Alternator should not "bog-down" your engine unless it's running in
a "Full-Field" condition, with no Voltage-Regulation,
in which case, it will destroy your Battery very quickly.

No kind of Alternator should cause unusual drag on the Engine while Starting.
Something else may be happening.

You'll need to provide a lot more information if You actually want a solution to your problem.
Especially Pictures of the installation, and a specification-Sheet for the Alternator.

Many modern Automotive-Alternators are designed to be regulated by the Car's Engine-Computer,
this may be your problem.
Most of them can either be modified to work without an Engine-Computer,
or an External-Voltage-Regulator can be Custom-Made for it.

An "Old-School" General-Motors-Alternator,
sometimes referred to as a "One-Wire-Alternator",
is a "Bolt-In-&-Go" trouble-free solution,
but it's a great deal more Powerful than what You may need,
that is, unless You intend to run some "High-Current" 12-Volt-Accessories, or Power-Tools
with your "Yard-Buggy", in that case, it would be quite appropriate and very-useful.
It would also mean that it would have enough Power to charge a dead Car-Battery.
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Thread Starter

Denny B

Joined Aug 30, 2022
11
Thank you for the reply.

I will be the first to admit that my cheap, Chinese alternator from Amazon might be the problem. It is a "one wire" alternator.
This is the alternator: Amazon.com: New Alternator Replacement For Mini 1 wire install with Volt Set Only 5.5 Pounds 35 AMP 1002111660, 1002111660, AND0525, 40052062 : Automotive

I went with the "Mini" alternator because of its smaller size and lower output of 35 AMPS. I don't know if it matters but the way I have it installed it is rotating "clockwise". It did not arrive with any paperwork or spec sheet.

At the moment I have the buggy disassembled for painting and the engine and alternator are not installed. But, I do have photos of when I was mocking it up for installation. Here is a photo of how it is installed in the buggy. Since this photo was taken I have installed a bracket from the top hole of the alternator to the buggy frame. (Don't be confused by that large, black cable to the lower left of the alternator. That is a rear brake cable that is running below the alternator).


Alternator 2.jpg

Here is a photo of the buggy.


20220825_152340.jpg

The battery is located inside that ammo box. I have a #8 wire running from the battery + post to the starter solenoid and a #8 wire running from the battery + post to the alternator output terminal.

When the engine is running and I attach the alternator wire to the battery it reads 14.7v.

Thanks for any help you can provide.
 

crutschow

Joined Mar 14, 2008
34,826
What's the diameter of that engine pulley?
If it's too large you may be over-speeding the alternator which can cause excessive low-speed drag, so you may need a larger pulley on the alternator.
A typical alternator should spin at about 2400 RPM at idle.
For that the alternator pulley diameter should likely be at least 1/3 of the engine pulley diameter.
From the picture, it looks like it's a lot less than that.

A larger pulley will, of course, reduce the low speed load from the alternator.
 

Thread Starter

Denny B

Joined Aug 30, 2022
11
I've actually thought about the difference in size between the two pulleys, but I never thought it would cause any problems. I will measure the pulleys tomorrow and let you know what I find.

The engine pulley is part of the CVT clutch and cannot be changed.

After I get the buggy back together I will change the alternator pulley to a larger size and post the results.

Thank you.
 

LowQCab

Joined Nov 6, 2012
4,290
Just because the advertising blurb says "One-Wire", doesn't necessarily mean anything.
There doesn't appear to be readily accessible information on the actual requirements for this Alternator,
but apparently, it's a very common Japanese Part found on many low-end "Economy-Cars".

I would hazard a guess, that the problem You may be having is caused by
not having a "Voltage-Sense-Wire" connected to the Regulator.
This "may be" the connector marked "IGN" on the Regulator, ( see attached picture ).

The connection could possibly serve 2-purposes at the same time ......... or just one, or maybe the other.

1 )
It supplies ~12-Volts to the Regulator to give it a "kick-start" when the Engine first cranks.
Many Alternators will not "Self-Energize" until around ~5 or ~6-thousand RPMs, but if
You supply 12-Volts with a Switch to the Alternator, it will energize the Field instantly.

2 )
This Wire may act as a "Voltage-Sense" Wire for the Regulator,
and if it's not connected to the Battery, the Regulator will think that the Voltage is very Low
and go "Full-Field" ( maximum-Output ) permanently.

This would explain your "drag" problem.
What is the exact Voltage at the Battery when You are noticing "drag" ?,
it should not be over 14.5-Volts, ( ~exactly 14-Volts would be more appropriate ).
If the Voltage is over 14.7-Volts, then I'm guessing that You need to connect the "IGN" terminal
to an Ignition-Switch, going to the Battery, and turn it "On" BEFORE starting the Engine.
Just the way it would be hooked-up in a Car.
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Denso Voltage Regulator .jpg
 

Thread Starter

Denny B

Joined Aug 30, 2022
11
Good Morning,

Okay...I did my math.

The diameter of the engine pulley is 7.5". The diameter of the alternator pulley is 3".

If I did my math correctly, the circumference of the engine pulley is 23.55" and the circumference of the alternator pulley is 9.42".

If I am correct, that would mean the alternator is rotating 2.5 times faster than the engine.

So, if the engine is idling at 1000 RPM the alternator is rotating at 2500 RPM.

I have no idea what the engine cranks at or idles at but your point is well taken about the difference in the pulley sizes may be the cause of the problem.

When I reassemble the buggy I will install a larger pulley on the alternator. I'm almost thinking I should try to find a 7" pulley.

What are your thoughts on that?

Thanks again.
 

crutschow

Joined Mar 14, 2008
34,826
So, if the engine is idling at 1000 RPM the alternator is rotating at 2500 RPM.
That sounds about right, so I see no need to change the pulley size.
A larger alternator pulley may mean it would not charge at idle.

The problem may be, as LQC pointed out, that you need one or more wires from the ignition switch or battery to the alternator connector for proper operation of the alternator.

This is in the product description:
NOTE 1: T-plug connection, B+ connection at 12:00
This would suggest that you need a battery connection to that terminal.

I found the diagram below, similar to what LQC posted, which shows that, for a Type 1 connector (which your alternator appears to have), one terminal goes to the Ignition Switch, and one goes to the Warning Light.
I suggest you connect both.
The warning light can be a 12V 2-3W, 12V incandescent automobile bulb.
If you use an LED type, you may have to add a resistor in parallel (say 50Ω, 5W) so it will carry the necessary starting field current for the alternator.

1662055518187.png

1662055265754.png
 

LowQCab

Joined Nov 6, 2012
4,290
The Pulley-Sizes are fine, don't mess with them.
Just make sure that the Belt is not too tight,
You should be able to press with your thumb, on the Belt, half-way between the Pulleys,
and get approximately 3/4" to 1" of Belt deflection.

But what is more important, is reporting the actual operating Voltages that have been measured.
Preferably, a DC-Amp-Clamp-Meter should be used to measure
the Current flowing between the Battery and the Alternator,
this would provide more information, and
eliminate some guess-work caused by only knowing the Voltages present.
You can get one at Harbor-Freight.

Right now, You don't really know if the Alternator is Wired appropriately or not.
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.
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Thread Starter

Denny B

Joined Aug 30, 2022
11
This is all great information. I thank both of you. I started painting the frame today and will try to have the engine and alternator back in by early next week and proceed with your suggestions. I'll see if the auto parts store has a regulator and go from there.

I will keep you guys posted.

Thanks again
 

Thread Starter

Denny B

Joined Aug 30, 2022
11
Okay, I just realized that I don't need the voltage regulator because it's already in the alternator. Right?

I just need to install the wires from the "T" shaped connector on the back of the alternator. Right?

Here is the interesting part. When I first came across this problem I went to a NAPA auto parts store and asked about that connector on the rear of the alternator and they did not know anything about it. I also asked if they had that "T" shaped connector and they had one but it was too big.

When I go to install the wires I will just use spade terminals.
 

Thread Starter

Denny B

Joined Aug 30, 2022
11
Okay, here is a "Semi Update"....I took the alternator to a good old fashion alternator shop here in Ocala, FL. They've been in business in the same little building since 1965 and it was just like going back in time! Anyway, I asked the guy if he would check out the alternator and I told him the back story of why I was there.

He checked it out and said it was a "Definite" one wire alternator meaning that the 2 terminals on the back (where the connector goes) are "inactive" and did not connect to anything. The "only" connections for this alternator are the output terminal and the case ground. He also said it was putting out 14.7v which we already knew because that's what I was getting at the battery. He also mentioned that he recommends14.2v for a 12v alternator.

After a little discussion we decided to replace the regulator with a 14.2v unit and he would wire it up so that the 2 terminals in the back of the alternator are active. One would be the exciter terminal and the other for the charge light.

After I get it back I will post the results.

_________________________________________________________________________________________________________________________________

Okay...I forgot to mention a couple of things. After my last post and before I took it to alternator shop, I wired up the alternator per the above diagram (and a couple others) and nothing made any difference. Still cranked slow and loaded up the engine. Also, I never did get the charging light to come on. I also took voltage readings at the battery while cranking with and without the alternator hooked up. The alternator was putting out voltage while cranking. That's what made me decide to visit the alternator shop.

PS: I found the "mini" connector for the rear terminals on Amazon. :)
 

crutschow

Joined Mar 14, 2008
34,826
You are aware that most car alternators use somewhere around 15HP to power them in a car?
That seems a little excessive for an alternator that likely generates not much more than a kW of electrical power.
But the TS's alternator is smaller so will take less power anyway.
 
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